Method and composition for cleaning aluminum magnesiumand alloys thereof

ABSTRACT

THE INVENTION DISCLOSED IS FOR A METHOD AND COMPOSITION FOR CLEANING ALUMINUM, MAGNESIUM, AND ALLOYS THEREOF BY USING A STABLE FORMED OF PARTICULAR AMOUNTS OF WATER, LIQUID AROMATIC HYDROCARBON, FATTY ACYL SARCOSINE OR SALT THEREOF, ALKALI METAL PYROPHOSPHATE, LINEAR ALKYL BENZENE SULFONATE, TERPENE, AND OPTIONALLY A COUPLING AGENT.

United States Patent Oflice US. Cl. 252-525 1 Claim ABSTRACT OF THE DISCLOSURE The invention disclosed is for a method and composition for cleaning aluminum, magnesium, and alloys thereof by using a stable emulsion formed of particular amounts of water, liquid aromatic hydrocarbon, fatty acyl sarcosine or salt thereof, alkali metal pyrophosphate, linear alkyl benzene sulfonate, terpene, and optionally a coupling agent.

This application is a continuation-in-part of US. Ser. No. 663,539, filed Aug. 28, 1967, now abandoned.

The present invention relates to a new improved method and composition for cleaning aluminum, magnesium, and alloys thereof. The invention provides a new stable emulsion formed of particular amounts of water, liquid aromatic hydrocarbon, fatty acyl sarcosine or salts thereof, alkali metal pyrophosphate, alkali metal linear alkyl benzene sulfonate, terpene, and optionally a coupling agent.

Numerous compositions are available to the art for cleaning metal surfaces. In instances where the surface is formed of an iron alloy or related durable metal, concern is seldom expressed for metal attack by even the strongest cleaning compositions. However, because surfaces formed of aluminum, magnesium or their alloys are highly sensitive and subject to attack by most otherwise effective cleaning compositions, special cleaning materials must be formulated. Not only must these special cleaning materials possess the property of effective cleaning, but also they must provide effective cleaning without attack on the metal surface.

Typically, exterior surfaces of piston and jet aircraft, and to an increasing extent, outer surfaces of trains, trucks, buses and the like include substantial amounts of aluminum alloys such as copper-aluminum alloys and magnesium alloys which are highly sensitive to most cleaning compositions. Cleaning these metal surfaces without corroding them is a major problem. Prior to this invention, water-soluble salts such as chromates, silicates, borates, and nitrates have been incorporated into metal cleaners to inhibit metal corrosion. Undesirably, chromates cause skin irritation and present a constant hazard to sensitive areas such as eyes of operating personnel. Since high concentrations of these corrosion inhibiting salts are generally required in this known type cleaner, great difficulty has been encountered in formulating cleaning compositions containing these salts in solution and avoiding surface residues of these salts in cleaning op erations. Furthermore, this type cleaner and particularly the chromate-containing cleaners have presented serious disposal problems.

It has now been found by practice of the present invention that a composition and method are provided for non-corrosive cleaning of aluminum and magnesium alloy surfaces using a solvent cleaner which is non-toxic. Further advantages of the present composition and method include substantial freedom from residue and solubility problems, while at the same time disposal difficulties are essentially eliminated. Practice of this invention provides 3,634,338 Patented Jan. 11, 1972 more eflicient and safer means for cleaning these surfaces, and overcomes many of the problems encountered using related prior art cleaners and methods.

Generally stated, the method of the present invention includes applying a mixture of one part by weight of an aqueous solvent composition with from about 1 to about 25 parts by weight of a diluent selected from the group consisting of water, aliphatic liquid hydrocarbons, aromatic liquid hydrocarbons, chlorinated liquid hydrocarbons, and mixtures thereof to the surface to be cleaned, and thereafter rinsing the surface. The new aqueous solvent composition of this invention includes about 5 to about 50 parts by weight of an aromatic hydrocarbon liquid, about 1 to about 10 parts by weight of a member selected from the group consisting of higher fatty acyl sarcosines, and alkali metal and ammonia salts thereof, about 1 to about 10 parts by weight of a tetra-alkali metal pyrophosphate, about 5 to about 30 parts by weight of an alkali metal linear alkyl benzene sulfonate having from about 6 to about 18 carbons in the alkyl group, about 1. to about 6 parts by weight of a liquid terpene, and from 0 to about 15 parts by weight of a coupling agent.

The aqueous solvent composition is a stable emulsion concentrate appearing similarly to the type known in the art as oil-in-water emulsions. The present stable emulsion has a pH in a range of about 8 to about 10 and preferably about 9 to about 9.5 in use dilution of about I to about 10 weight ratio of water diluent to emulsion concentrate.

Except in some instances, it is critical that the present emulsion mixture be used in the range of about pH 8 to about pH 10. At pH values above about 10, the mixture often exhibits a tendency to attack metals such as aluminum, magnesium, and alloys thereof. At pH values below about 8, and in a few instances even below about 8.5, the typically excellent emulsion stability of the present mixture may disappear.

In the present method for removing soils found on surfaces of aluminum, magnesium, and their alloys, such as on the exterior surfaces of military and commercial aircraft, buses, trains and the like, a mixture of one part of an aqueous solvent composition with from about 1 to about 25 parts by weight, and preferably from about 1 to about 10 parts by weight of a liquid diluent is applied to the soiled surfaces. The diluents may be water, aliphatic liquid hydrocarbons, aromatic liquid hydrocarbons, chlorinated liquid hydrocarbons and mixtures thereof, as well as other polar and non-polar organic liquids. Preferably, the cleaning mixture is one part of the aqueous solvent composition to form about 5 to about 25 parts by weight of water where water is the diluent, and from about 1 to about 10 parts by weight of one or more of the organic diluents.

Suitable aromatic hydrocarbon diluents include benzene, toluene, xylene, Aromatic Solvent (a mixture of aromatic hydrocarbons having a flash point of 150 F.), and the like. Suitable aliphatic hydrocarbon diluents include kerosene, diesel fuel, mineral spirits, mineral seal oil, Stoddard solvent, No. 1 fuel oil, and the like. Suitable chlorinated hydrocarbon diluents include chlorinated aliphatic compounds such as carbon tetrachloride, perchloroethylene, trichloroethylene, tetrachloroethylene, and chlorinated aromatic compounds such as orthodichlorobenzene.

The aqueous solvent composition of this invention appears as a dilutable emulsion concentrate including particular amounts of aromatic solvent and other critical components. The other particular components include, essentially, fatty acyl sarcosine, alkali metal pyrophosphate, alkyl benzene sulfonate, water, and optionally, a coupling agent and ammonia.

The aromatic solvent in the concentrated solvent emulsion is an aromatic liquid hydrocarbon such as benzene, toluene, xylene, Aromatic 150 Solvent, and petroleum fractions having at least 50 percent aromatic content. The solvent preferably has a flash point of above 100 F. The aromatic solvent component is included in an operable amount from about 5 to about 60 parts, and preferably, from about 35 to about 55 parts.

Alternatively, aliphatic liquid hydrocarbons or chlorinated liquid hydrocarbons may be substituted in whole or in part for the aromatic solvent component. Suitable aliphatic solvents include kerosene, diesel fuel, mineral spirits, mineral seal oil, Stoddard solvent, No. 1 fuel oil, and the like. Suitable chlorinated hydrocarbons include chlorinated aliphatic compounds such as carbon tetrachloride, perchloroethylene, trichloroethylene, tetrachloroethylene and the like, and chlorinated aromatic compounds such as orthodichlorobenzene and the like. Preferably, however, the solvent is principally liquid aromatic hydrocarbons.

The fatty acyl sarcosine component is preferably higher fatty acyl sarcosine, and alkali metal and ammonium salts thereof. The fatty acyl group may have from about 8 to about 18 carbons. The preferred sarcosine is sodium lauryl sarcosine. This surfactant aids in inhibiting corrosion of the magnesium or aluminum containing metal surfaces from which soil is removed by the method of this invention. The sarcosine component is included in an operable amount from about 1 to about 10 parts, and preferably from about 1 to about 5 parts.

The pyrophosphate component includes tetrasodium and preferably tetrapotassium pyrophosphate. This condensed phosphate functions to inhibit corrosion of a wide variety of aluminum and magnesium alloys including those which are attacked by acidic and high alkaline mixtures even in the absence of the chromate ion. The pyrophosphate component furthermore aids in emulsification, detergent action and soil flocculation in the present method. The pyrophosphate component is included in an operable amount from about 1 to about 10 parts, and preferably from about 1 to about 2 parts.

Another critical component in the present emulsion concentrate is an alkali metal alkyl benzene sulfonate having from about 6 to about 18 carbon atoms. Preferably, the alkyl group is a linear group having from about 8 to about 14 carbons. This compound tends to essentially eliminate viscosity problems and crystal formation which are normally encountered in mixtures of aromatic solvents and fatty acid soaps. The preferred alkyl benzene sulfonate is the potassium salt. The alkyl benzene sulfonate may be added either as the alkali metal salt or free ac d form. Where the free acid is added, a quantity of alkali metal hydroxide preferably is also added to neutralize the acid. About 5 parts potassium hydroxide, for example, is usually sufficient. The sulfonate component is included in an operable amount from about 5 to about 30 parts, and preferably from about 10 to about 20 parts.

The terpene which is added is liquid terpene such as terpentine, alpha pinene, pine oils such as Yarmour pine oil, and the like. The liquid terpene improves solvency and enhances cleaning composition penetration power. The terpene component is preferably included in an operable amount from about 1 to about 6 parts.

Water is included as an essential component of the emulsion cleaning concentrate in an operable amount from about 5 to about 50 parts, and preferably from about 15 to about parts.

An optional component in the emulsion cleaning concentrate is the coupling agent. Coupling agents for this use are well-known in the art and include such compounds as ethylene glycol monobutyl ether, monohydric and polyhydric alcohols having from 3 to 6 carbon atoms, diethylene glycol monoalkyl ether having from 2 to 4 carbon atoms in the alkyl group. A preferred coupling agent is a monohydric alcohol such as Cyclohexanol. The coupling agent functions to maintain the various components in the cleaning composition in a stable form, tending to prevent separation of the aqueous and organic solvent components. The coupling component may optionally be included in an operable amount of as much as about 15 parts, and preferably is included in an amount from about 1 to about 6 parts.

The emulsion cleaning concentrate may also include up to one part and preferably about 0.1 to about 0.2 part of concentrated aqueous ammonia. Ammonia is important in the storage of the cleaning composition for inhibiting corrosion of steel in the head space of containers which may be used for the composition.

Rinsing in the method of this invention is preferably effected using water although both polar and non-polar organic liquids may also be used. The rinse liquid may be a non-corrosive liquid, and is preferably selected from the group of diluent liquids which may be present in the cleaning mixture used.

Both the cleaning and rinsing steps of this method are preferably carried out by spraying the respective liquids onto the surfaces to be cleaned. Alternatively, the liquids may be applied by hand with or without rubbing the surfaces being cleaned. Almost any spray cleaning equipment may be used in the present method, including many types of spray equipment which are well-known in the art. Excellent cleaning may be effected conveniently and in relatively short time even when the cleaning composition and the surfaces to be cleaned are at ambient temperature i.e., about 65 F. to about 80 F.

This invention is further illustrated by the following non-limiting examples. In this description, including the examples which follow, all components are added as parts by weight unless otherwise specified.

EXAMPLE 1 An aqueous solvent mixture composition having components in the amounts shown below, when diluted with 5 and 10 parts water per part of emulsion composition had a pH of about 9.2 to about 9.3. These diluted emulsions at about F. to about F. were sprayed against soiled jet aircraft surfaces formed of aluminum, magnesium, aluminum-copper alloy and a magnesium alloy. The surfaces were then rinsed with water. Highly effective cleaning was obtained without corrosion of the metal surfaces and without damage to painted portions of the surfaces. The emulsion stability was excellent.

Aqueous solvent mixture (cleaning emulsion concentrate) Approximate Component: weight percent Water 17.1 Linear alkyl benzene sulfonic acid a 16 Potassium hydroxide (45% active) 6.5 Tetrapotassium pyrophosphate 2 Pine oil 4.5 Cyclohexanol 3.5 Aromatic solvent 45.2 Sodium lauryl sarcosinate 5 Aqueous ammonia 0.2

Distribution of carbons in alkyl groups: 9 carbon atom chains, 0.1 percent: 10 carbon atom chains, 7.8 percent; 11 carbon atom chains. 55.9 percent; 12 carbon atom chains, 31.2 percent; 13 carbon atom chains, 5.0 percent.

EXAMPLE 2 The procedure of Example 1 was repeated except the composition used was modified by changing the amount of the sulfonic acid component and the potassium hydroxide component such that the use dilutions with 5 and 10 parts water per part of emulsion concentrate had a pl-I of about 7. Poor emulsion stability was noted. The cleaning performance was rated as poor relative to the cleaning performance of Example 1.

5 EXAMPLE 3 The procedure of Example 2 was repeated except the use dilution pH was about 11. Although good emulsion stability was noted, application of this composition by the procedure of Example 1 was eflected with severe attack of the aluminum, magnesium and alloy surfaces noted.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that various modifications may be made therein without departing from the spirit or scope of the present invention.

What is claimed is:

1. A stable emulsion cleaning composition for cleaning surfaces of aluminum, magnesium, and alloys thereof which consists essentially of 17 weight percent water, 16 weight percent linear alkyl benzene sulfonic acid wherein the alkyl group has from 9 to 13 carbon atoms, 6.5 weight percent of a 45 percent by weight aqueous solution of potassium hydroxide, 2 weight percent tetrapotas- 2O sium pyrophosphate, 4.5 weight percent pine oil, 3.5 weight percent cyclohexanol, 45 weight percent solvent mixture of aromatic hydrocarbons having a flash point of 150 F., 5 weight percent sodium lauryl sarcosinate,

0.2 weight percent of concentrated aqueous ammonia, 5

said weight percents being approximate, and said emulsion cleaning composition having a pH in the range of about 9 to about 9.5 when diluted with 10 parts by weight of water per part by weight of said emulsion.

References Cited UNITED STATES PATENTS 3,538,006 11/1970 Benson et a1. 252-137 3,367,878 2/1968 Mankowich 252-139 X 3,146,207 8/1964 Rosenfeld et al 252-118 3,123,566 3/1964 Kramer et a1. 252-139 3,085,982 4/1963 Steer et a1 -1 252-137 3,057,804 10/1962 Berkeley et a1. 252-118 2,948,685 8/1960 Fisher 252-118 2,901,433 8/1959 Spring 252-118 2,700,654 1/1955 Holman 252-118 2,374,113 4/1945 Lowe 252-118 OTHER REFERENCES McCutcheons Detergents and Emulisfiers, 1963, p. 126.

LEON D. ROSDOL, Primary Examiner D. L. ALBRECHT, Assistant Examiner US. Cl. X.R. 

